Revenue - Revenue by Major Species (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue from External Customer [Line Items]
Revenues		$ 1,674	$ 1,584	$ 1,547	$ 1,455	$ 1,564	$ 1,480	$ 1,415	$ 1,366	$ 6,260	$ 5,825	$ 5,307
Operating Segments | United States Segment
Revenue from External Customer [Line Items]
Revenues										3,203	2,877	2,620
Operating Segments | International Segment
Revenue from External Customer [Line Items]
Revenues	[1]									2,972	2,890	2,643
Livestock
Revenue from External Customer [Line Items]
Revenues										3,030	3,154	3,037
Livestock | United States Segment
Revenue from External Customer [Line Items]
Revenues										1,219	1,269	1,244
Livestock | International Segment
Revenue from External Customer [Line Items]
Revenues										1,811	1,885	1,793
Companion Animal
Revenue from External Customer [Line Items]
Revenues										3,145	2,613	2,226
Companion Animal | United States Segment
Revenue from External Customer [Line Items]
Revenues										1,984	1,608	1,376
Companion Animal | International Segment
Revenue from External Customer [Line Items]
Revenues										1,161	1,005	850
Contract Manufacturing and Human Health Diagnostics [Member]
Revenue from External Customer [Line Items]
Revenues										$ 85	$ 58	$ 44

[1] Revenue denominated in euros was $742 million in 2019, $745 million in 2018, and $660 million in 2017.